<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        /*结构伪类选择器*/
        li:first-child{
            color: red;
        }
        li:last-child{
            color: greenyellow;
        }
        li:nth-child(3){
            color: #cd65e4;
        }
        li:nth-last-child(2){
            font-size: 20px;
        }
        /*所有的偶数变大*/
        li:nth-child(2n-1){
            font-size: 30px;
        }
    </style>
</head>
<body>
<ul>
    <li>123</li>
    <li>123</li>
    <li>123</li>
    <li>123</li>
    <li>123</li>
    <li>123</li>
    <li>123</li>
    <li>123</li>
    <li>123</li>
</ul>
</body>
</html>